• Progress in Superconductivity
• /
• v.12 no.1
• /
• pp.12-16
• /
• 2010

We have measured the trapped field of YBCO bulk with different configuration by applying the magnetic field of $Nb_3Sn$ superconducting magnet. Initially the circular type of YBCO bulk superconductor was prepared and then hole, parallel to the c-axis and located at the center of bulk was mechanically drilled. The YBCO bulk with hole was filled with resin. Typical size of hole in YBCO bulk was 10 mm in diameter. Trapped field characteristics were compared with different specimen conditions. Our preliminary result indicates the increment rate of trapped field, 0.232 kG, measured on the YBCO without hole was much higher than that, 0.011 kG, measured on YBCO with hole.

• Proceedings of the KIEE Conference
• /
• 2003.07b
• /
• pp.900-902
• /
• 2003

Critical current($I_c$) degradation of HTS tapes after bending is one of the holiest issues in HTS development and application studies. Many people are measuring $I_c$ degradations for effect of tending radius. However even if the bending radius is larger than the breaking radius a HTS tapes can be damaged by repetitive bending, which is unavoidable in the winding processes. Therefore, We studied the $I_c$ degradation after repetitive bending, at 77K with self-field, of Bi-2223 tapes processed by "Powder-in-Tube" technique, which was made by America Superconductor Corporation(AMSC), Innova Superconductor Technology(InnoST) and Korea Electro-technology Research Institute(KERI). For each specimen $I_c$ degradation was measured various bending radius as function of repetitive bending number.

• Progress in Superconductivity and Cryogenics
• /
• v.12 no.1
• /
• pp.1-5
• /
• 2010

Silver stabilizing layer of coated conductor has been prepared by dip coating method using organic silver complexes containing 10 wt% silver as a starting material. Coated silver complex layer was dried in situ with hot air and converted to crystalline silver by post heat treatment in flowing oxygen atmosphere. A dense continuous silver layer with good surface coverage and proper thickness of 230 nm is obtained by multiple dip coatings and heat treatments. The film heat treated at $500^{\circ}C$ showed good mechanical adhesion and crystallographic property. The interface resistivity between superconducting YBCO layer and silver layer prepared by dip coating was measured as $0.67\;{\times}\;10^{-13}\;{\Omega}m^2$. Additional protecting copper layer with the thickness of $20\;{\mu}m$ was successfully deposited by electroplating. The critical current measured with the specimen prepared by dip coating and sputtering on same quality YBCO layer showed similar value of ~140 A and proved its ability to replace sputtering method for industrial production of coated conductor.

• Journal of the Korean Chemical Society
• /
• v.36 no.1
• /
• pp.16-23
• /
• 1992

High $T_c$, superconductor $(Y_{1-x}Eu_x)Ba_2Cu_3O_{7-{\delta}}$ (x = 0.0, 0.2, 0.4, 0.6, 0.8, 1.0) were prepared and the physical properties were observed. XRD analysis showed that the structures of all the specimen were orthorhombic and the lattice parameters a, b and c increased with the increasing x value. Electrical resistivity and magnetization measurements revealed that pure high $T_c$, superconducting phases were formed at above 90 K. The critical temperatures increased with increasing the amount of Eu. From the measurement of magnetization and the size of the grains using SEM micrographs, volume diamagnetic susceptibilities for each specimen were calculated. These values decreased with the increasing x value. The composition of Ba in the lattice site decreased as the concentration of Eu increased, and this was confirmed by EPMA. It was found out that the volume diamagnetic susceptibility of each specimen was directly influenced by the composition of Ba in the lattice site.

• Journal of Powder Materials
• /
• v.9 no.5
• /
• pp.359-364
• /
• 2002

We report the structure, thermal and magnetic properties of a non-equilibrium $Al_{0.6}(Fe_{50}Cu_{50})_{0.4}$ alloy powder produced by rod milling and chemical leaching. An X-ray diffractometry(XRD), a transmission electron microscope(TEM), a differential scanning calorimeter(DSC), a vibrating sample magnetometer(VSM), and superconducting quantum interference device(SQUID) were utilized to characterize the as-milled and leaching specimens. The crystallite size reached a value of about 8.82 nm. In the DSC experiment, the peak temperatures and crystallization temperatures decreased with increasing milling time. The activation energy of crystallization is 200.5 kJ/mole for as-milled alloy powder. The intensities of the XRD peaks of as-milled powders associated with the bcc type $Al_{0.5}Fe_{0.5}$ structure formative at $350^{\circ}C$ sharply increase with increasing annealing temperature. Above $400^{\circ}C$, peaks alloted to $Al_{0.5}Fe_{0.5}$ and $Al_{5}Fe_{2}$ are observed. After annealing at $600^{\circ}C$ for 1h, the leached Ll specimen transformed into bcc $\alpha$-Fe and fcc Cu phases, accompanied by a change in the structural and magnetic properties. The saturation magnetization decreased with increasing milling time, and a value of about 8.42 emu/g was reached at 500 h of milling. The coercivity reached a maximum value of about 142.7 Oe after 500 h of milling. The magnetization of leached specimens as function of fields were higher at 5 K, and increased more sharply at 5 K than at 100 K.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.11 no.2
• /
• pp.154-161
• /
• 1998

The effects of melting temperature and holding time on the critical current density($J_c$) of $YBa_2Cu_3O_x$ based superconducting bulk fabricated by MPMG process were investigated. The amount of the formed $Y_2BaCuO_5$ phases increased with the melting temperature. However, the value of critical current density was highest at 1120 $^{\circ}C$. With this proper melting temperature, the effect of holding time on the critical characteristics was also investigated. In the case of Ag addition, the volume of the formed $Y_2BaCuO_5$ phase when the amount of Ag addition was 10 wt% and 20 wt% was observed to be highest at 20 minute and 40 minute respectively. But in the specimen without Ag, volume of $Y_2BaCuO_5$ phase increased as the holding time increased. The proper melting temperature and the holding time obtained were 1120 $^{\circ}C$ and 20 minute. The long holding time was not effective for the $J_c$ improvement as well as the formation of $Y_2BaCuO_5$.

• Korean Journal of Materials Research
• /
• v.5 no.7
• /
• pp.880-887
• /
• 1995

Melt spun YB $a_2$C $u_3$A $g_{15}$ and YbB $a_2$C $u_3$A $g_{x}$(x=5, 16 and 53) precursor alloy ribbons were oxidized at 263~322$^{\circ}C$, and heat-treated at 872~89$0^{\circ}C$ under 1.0atm oxygen pressure. In addition, about ten ribbons were stacked and coupled by pressing, and then followed the same heat treatment. YB $a_2$C $u_3$ $O_{7-{\delta}}$(1-2-3) or YbB $a_2$C $u_3$ $O_{7-{\delta}}$(1-2-3) phase was formed in both the ribbons and the multilayered specimens. The formed 1-2-3 phases were not texturized in all the ribbons, but slightly texturized in the multilayered specimens. $J_{c}$ was not achieved in all the ribbons at 77K and zero magnetic field. Among the multilayered specimens, YB $a_2$C $u_3$A $g_{15}$ and YbB $a_2$C $u_3$A $g_{16}$ showed $J_{c}$ of 260 and 180A/$\textrm{cm}^2$, respectively. YB $a_2$C $u_3$A $g_{15}$ and YbB $a_2$C $u_3$A $g_{16}$ are considered to be the appropriate compositions in producing textured superconducting oxides with improved $J_{c}$ by pressing. Onset critical temperature ( $T_{on}$ ) of the multilayered YB $a_2$C $u_3$A $g_{15}$ was 92K while those of YbB $a_2$C $u_3$A $g_{x}$(x=5 , 16 and 53) were 88~90K. , 16 and 53) were 88~90K.